How many miles do you get on a full tank?

[x5pilot]

Hi guys,
I know we all drive differently and our driving styles change with our moods, however I was wondering on average how many miles you get from a full tank down to say 30 miles left on your fuel warner?
I drive a 4.4 and most of the time drive with a "heavy foot", I guess I get between 400 and 430 miles on highway driving at an average speed of 80-90mph.
We can all look at the BMW mpg values but I'm looking for tank figures - cant seem to find anything on the web.

I'm particularly interested in diesel stats as my X5 is up for replacement in April and need to look around.

Thanks